1. Field of the Invention
The present invention relates to pneumatic tires and more particularly to an improvement of tread patterns of pneumatic tires used for relatively small construction vehicles which travel on soft ground of high water content, e.g., loam soil.
2. Prior Art
Heretofore, pneumatic tires used for small construction vehicles traveling on soft ground have been devised so as to receive the buoyancy of soft ground, namely, so as to float on the soft ground. The tractive force was obtained by making use of shear resistance generated when tires press and harden mud in the grooves of the tread pattern. In order to obtain a strong tractive force, the grooves of the tread pattern had a large width and a great depth and the round edges of grooves had a large radius of curvature.
Besides the above, there were provided with lug 2 and groove 3 having a large backward angle .alpha. directed from a neighborhood of the equatorial line TE of the tire toward the tread side line SL as shown in FIG. 1 in order to facilitate the discharge of the mud clogged in the grooves. Such tires are used by limiting the rotation to one direction.
But prior art tires having such tread patterns are still weak in their tractive force, lack in wear resistance and are susceptible to external damages such as chips, cuts, etc. Thus, the durability of prior art tires is not satisfactory.